Substitute facade example with a better one

patterns/structural/facade.py

@@ -2,6 +2,9 @@
 # -*- coding: utf-8 -*-
 
 """
+Example from https://en.wikipedia.org/wiki/Facade_pattern#Python
+
+
 *What is this pattern about?
 The Facade pattern is a way to provide a simpler unified interface to
 a more complex system. It provides an easier way to access functions
@@ -13,17 +16,6 @@
 serves as an unified interface to all the underlying procedures to
 turn on a computer.
 
-*What does this example do?
-The code defines three classes (TC1, TC2, TC3) that represent complex
-parts to be tested. Instead of testing each class separately, the
-TestRunner class acts as the facade to run all tests with only one
-call to the method runAll. By doing that, the client part only needs
-to instantiate the class TestRunner and call the runAll method.
-As seen in the example, the interface provided by the Facade pattern
-is independent from the underlying implementation. Since the client
-just calls the runAll method, we can modify the classes TC1, TC2 or
-TC3 without impact on the way the client uses the system.
-
 *Where is the pattern used practically?
 This pattern can be seen in the Python standard library when we use
 the isdir function. Although a user simply uses this function to know
@@ -40,84 +32,66 @@
 """
 
 from __future__ import print_function
-import time
-
-SLEEP = 0.1
-
-
-# Complex Parts
-class TC1:
-    def run(self):
-        print(u"###### In Test 1 ######")
-        time.sleep(SLEEP)
-        print(u"Setting up")
-        time.sleep(SLEEP)
-        print(u"Running test")
-        time.sleep(SLEEP)
-        print(u"Tearing down")
-        time.sleep(SLEEP)
-        print(u"Test Finished\n")
-
-
-class TC2:
-    def run(self):
-        print(u"###### In Test 2 ######")
-        time.sleep(SLEEP)
-        print(u"Setting up")
-        time.sleep(SLEEP)
-        print(u"Running test")
-        time.sleep(SLEEP)
-        print(u"Tearing down")
-        time.sleep(SLEEP)
-        print(u"Test Finished\n")
-
-
-class TC3:
-    def run(self):
-        print(u"###### In Test 3 ######")
-        time.sleep(SLEEP)
-        print(u"Setting up")
-        time.sleep(SLEEP)
-        print(u"Running test")
-        time.sleep(SLEEP)
-        print(u"Tearing down")
-        time.sleep(SLEEP)
-        print(u"Test Finished\n")
-
-
-# Facade
-class TestRunner:
+
+
+# Complex computer parts
+class CPU(object):
+    """
+    Simple CPU representation.
+    """
+    def freeze(self):
+        print("Freezing processor.")
+
+    def jump(self, position):
+        print("Jumping to:", position)
+
+    def execute(self):
+        print("Executing.")
+
+
+class Memory(object):
+    """
+    Simple memory representation.
+    """
+    def load(self, position, data):
+        print("Loading from {0} data: '{1}'.".format(position, data))
+
+
+class SolidStateDrive(object):
+    """
+    Simple solid state drive representation.
+    """
+    def read(self, lba, size):
+        return "Some data from sector {0} with size {1}".format(lba, size)
+
+
+class ComputerFacade(object):
+    """
+    Represents a facade for various computer parts.
+    """
     def __init__(self):
-        self.tc1 = TC1()
-        self.tc2 = TC2()
-        self.tc3 = TC3()
-        self.tests = [self.tc1, self.tc2, self.tc3]
-
-    def runAll(self):
-        [i.run() for i in self.tests]
-
-
-# Client
-if __name__ == '__main__':
-    testrunner = TestRunner()
-    testrunner.runAll()
-
-### OUTPUT ###
-# ###### In Test 1 ######
-# Setting up
-# Running test
-# Tearing down
-# Test Finished
-#
-# ###### In Test 2 ######
-# Setting up
-# Running test
-# Tearing down
-# Test Finished
-#
-# ###### In Test 3 ######
-# Setting up
-# Running test
-# Tearing down
-# Test Finished
-#
+        self.cpu = CPU()
+        self.memory = Memory()
+        self.ssd = SolidStateDrive()
+
+    def start(self):
+        self.cpu.freeze()
+        self.memory.load("0x00", self.ssd.read("100", "1024"))
+        self.cpu.jump("0x00")
+        self.cpu.execute()
+
+
+def main():
+    """
+    >>> computer_facade = ComputerFacade()
+    >>> computer_facade.start()
+    Freezing processor.
+    Loading from 0x00 data: 'Some data from sector 100 with size 1024'.
+    Jumping to: 0x00
+    Executing.
+    """
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod(optionflags=doctest.ELLIPSIS)